Self sealing pneumatic tire



Sept. 22, 1959 J. M. SCHUTZ SELF SEALING PNEUMATIC TIRE 2 Sheecs-Sheet 2F'iled May 15. 1953 INVENTOR.

JSEFH Z"Z5C'HUTZ Application .May 113, 1953, Serial N0. 354,753 4Claims. (C1. 152-330) 'I'his invention relates to sealing compositionsused in puncture-healing artioles and mute particularly relates toartieles such a's tire inner tubes and tubeless gires providedinterhallyWith'hn element of pi1ridi1fehealing cornposition.

QI' l;e practiqe has b ee n tp proy id e cert ain.types of tire innertubes with a layer of a sealing composition in the ciown region thereofto heal punctures caused by penet'ration ofpoixited'objects through theair-ietaining wall. Stich practit:e has been continued with the adventof tubelass tir es wherein an element cwf sealing composition isa1iplied on the inside of the air retaining cavity in the 'crdwn regionof slich a tire to provide fo1 puncture healmg. Although natural rubberhas been used as the rubber hydrocarbon constituerit of the ccmpositionof such a sealant, for Various reasons it has been unsatisfactory andgenerally "a composition has been adopted comprisi.'ng a pzirtiallyvulcanized rubbery copolymer of a major frortign'of an isoolefin havingfrom 4 to 7 carbon atoms With a minor proportion of an open-chainconjugated diolefinhaving fro'm 4 to 8 carbonk1toms. Thi copolyniet 'isgenerailly known 'as Butyl mbber. Butyl rub 1'JCI conipositions althoughaceeptable for a Sealant in some respects, in the vulcanized state havevery poor adhesi on to adjacent tire portions cmprised cf rubberycompositions other than Butyl rubber unless expensive and'cpmplicatedste'ps are taken during n'1'anufactur'e to insur'e good adhesin.However, even With g'fezit care and laboribus effor't during tirebuilding, difiicnlty is expe'rienced in 'obtaining sufiicient adh'esionbetween a Bn tyl sealant and the adjacent tire portions to resist theStress of high centrifugal force during road operation of the'tire.

'Another problem in the use cf Butyl type sealants is that afterextended periods of tire operation the -sei=.lant surface craoks toproduce an undesirable 'appearance as Well as a lack of sealingprotection at the cracks.

An objeet bf the 'present invention, therefore, is to pro- Vid a sealingcompbsition which has improved p'roperfies of adhesion fo thevulca.nized rubbery components of a tire in addition to good puncturesealing charac'teristics.

Y'et anther object of this inventi0n is to p'rovide a sealing composition which Will rriaintain position in the crown of a tire or in thecrown of a tire tube despite the rigordus cefitrifugal actidn 0 frotation at high speed.

A furtherobjec't of this invention i s'to provide a puncturelialir'i'gxrticld comprised of a seziling cmposition of a copolyjmer ofbutadien6axid styren'e polymerized at relatively W teri1peratures, andcoi1tining an 1in1isually lar ge aniol'nit9fsdfte1ier and t ikifierl"Yet anotl1e'r Objct of this invei1tion is t0 provi de a seaili'n'gc'oxi1i bsitibri for tifeg r tire tubes With impr0 ved crack 1yesisjanceduring tire s'eiVice. T1i S'e nd t hiifqbjeete be more ne ad ily und erst9ocl refegeiide tg ithe prefe ii1ed fbrm c f the inv ent ion Pp.tented 0 Sept. 22, 1959 perspective of an inflatable self-healing article ofthe invention.

An article constructed in accordance with the foregoing objects of theinvention contains a sealing element comprised of a copolyrner of amajor proportion of butadiene and a rninor roportion of styrenecopolymerized at temperatures below 58 F. and coagulated with a quantitycf emulsified softener. Such a copolynier is comrnonly terrned oilextended cold rubber. While copolymers of butadiene and styrenecopolyrnerized at teinperatures 063 122 F. are not generallysatisfactory as sealant maten'als itl1as been fgund that.such a eopolymer coagulated with amou1its of softener at temperatures 11nder 58F. generally form good sealants ifproperly compounded With nnusually.large quantities of softener. Polymerization temperatures of 58 F. 41F., 14 F., 0 F. and 14 F. are particular examples of polymers which havebeen found satisfactory for the copolymers of the present inventionalthough the invention is not necessarily limited to these temperatures.

Referring to Figure 1, a tubeless tire generally indicated at 1 is showncomprised of bo dy pertion 2, inextensible bead portions 3 and 4 andtrcad element 5. T0 provide for retention 0f air Linder pressuie duringoperation of the tire on a vehicle, the entire inner snrface of the tireWhich defines the air retaining cavity is lined With a vulcanizedrubbery air impervios liner 6. Such liner may be comprised 0f eithernatural or syx;thet ic rubber. Sealant 7 covers the liner 6 over th at-su rf aee thereof which lies in the portion of the tire.nsnally desig-1 ited as the crown which is essentially adjaq nt tp .t he radcontacting surface cf the tread.

A puncture proof tube generally indicated at 9 is shown in Figure 2.Such a t ube i s c9mpr i sed of air impervious rubbery Wall 10 prdvidedwith'. valve 11 adapted for inflating the tube With air under pressure..The tnbe i s protected against.air loss fr0m pllnctureg by .sealantmember 12 in the crcgwncomprised of the novel comppsition to bedescribed hereinafter.

Fign1;e 3 s how san inflatable rubber ball pxovided with valve 31,flexible wall 32 and sealant layer 153 .to heal punctures. Figure 4illustrate s another inflatable article such as a childs -rubberswimming pool comprised 0 f inflation valve 40, flexible Wall 41 andsealant layer 42 dfbsigned to -heal punctures.

I-IOT AND GOLD NAIL TEST T0 determine the punctnre sealing characteristics f the sealant f fhe ini ention at diffe rent pendipions o f tem*Pefature, a tire is iiiiihted upon -a tes t wheel and rn n tlen mileisforiiarinupl Fr 8-penny nails then are ham- Inered into thetire and fhet es t wheel is ru n n 1i l es. The test"w)vh6el iS disriionted and after 30 minnt es ty vcp Qf t he nails ie i5ulled f ro n 1 ihe tire. Thetire and wheel as;embly is immersed in water to note any air escaping atthe'punctures. Results of t his tes ar e repor te d a5 bpt air lossresults and ar eindieated a5 godd, fif, or unsatisfactory.

After the hot air loss test, the tire is allowed tc eqol foi 18 hoursandfhe two remaining nails are Withdrawn. The tire and vyheel a ssemblyis again immersed in wa tet't d iiote any aii escaping frqn 1 the punctures and the results a1eereported as cld air l qsg results.

NAILBOARD TEST A tire provided With a sealant to be tested is mounted na wheel and driven over a board from which project six 8-penny nails.The tire is then immersed in water to note any less of air through thenail holes.

In all formulations given below parts are by weig-ht based 011 100 partsby weight of copolymer material in the cornposition.

Example 1 Parts Low temperature polymer 100.00 Softener l in polymer25.00 Iren oxide 37.50

Zins oxide 3.75 Softening 011 49.95 Tackifier and softener 37.50

Sulfur .80

Boric acid .50

Rubber accelerator .50 Rubber antioxidant 1.25

Addecl 1:0 copolymer during manufacture.

A sealant composition was mixed on a two-roll mill according to theabove formula and then shaped to the desired dimenslons to provide asealing element t0 fit the crown et the tire. The tire was vuleanizecland mounted on a test wheel and the aforementioned nailboard test andnail tests were run with satisfactory results.

Example 2 Parts Low temperature polymer 100.00 Softener 1 in pclymer37.50 Iren oxide 37.00 Zinc oxide 4.00 Rubber softener 50.00 Rubbertackifier and softener 40.00 Sulfur .80 Boris acid .50 RubberAccelerator .50 Rubber antioxidant 1.50

Added to copolymer during manufacture.

A sealant composition was mixed on a two-roll mill according to theabove formula and shaped to the dimensions to provide a sealing elementto fit the crown of a tire. The tire was vulcanized and mounted on atest wheel and the aforen1entioned nail tests were run with satisfactoryresults.

Added to copolymer during manufacture.

A sealant composition was mixed on a two-roll mill according to theabove formula and shaped to the desired dimensions to provide a sealingelement to fit the crown of a tire. The tire was vulcanized and mountedon a car wheel and the aforementioned nail tests were run withsatisfactory results.

4 ENDURANCE TEST Tubeless tires were built using a sealant composed ofthe composition of Example 1 over 180 of the inside crown surface by theband ply of eacl1 tire. The other 180 cf the inside crown surface cf theband ply was covered with a sealant composed of a conventional sealingcornposition comprised cf Butyl type rubber. The tires were run an atest wheel underinflated and everloaded for 6500 miles to compare thecracking and blistering characteristics cf each sealant. The results asfollow shew the improved perforrnance of the novel unusually high oilloaded low temperature polymerized butadiene-styrene polymer compound.

1 Control sealant is comprised essentially of Butyl rubber.

lt is thought that the novel composition attains its puncture sealingcharacteristics by clinging t0 the nail protruding through the tire bodyinto the air-containing cavity. As the nail is withdrawn the novelcornposition is pulled into the hole left by the nail thereby healingthe puncture and sealing the air-containing cavity against less of air.

The above formulae are given only as illustrations and it is to oeunderstood that variations in constituents may be n1ade by th0sefamiliar with the art cf rubber compounding. Per example, acceleratorand sulfur variations may be made to obtain an optirnum state ofvulcanization depending upon the inilatable article being Vulcanized asWell as upon the heat and time of vulcanization. I-Iowever, for bestpuncture-sealing, characteristics the sulfur content available forvulcanization should be between .2 and .80 part by weight based uponparts of copolymer.

In place of butadiene in the rubbery copolymer, other open-chainconjugated diolefins may be used such as piperylene, 2,3-dimethylbutadiene-l3; 3-methyl pentadiene-1,3; 2rnethyl pentadiene-l,3;hexadienel3; hexadiene-2,4; isoprene and others. In this invention theuse of butadiene-l3 and styrene are preferred, but not to be deerned aslimiting.

Aryl substituted ethylene monomers polymerizable with the diene monomerinclucle styrene, alpha methylstyrene, p-chloro styrene, p-methoxystyrene, vinyl naphthalene and others. In this invention styrene ispreferred but is not to be deerned lhniting.

The iron oxide content may be varied frorn 15 to 45 parts by Weight onthe copolyrner depending upon the type of tire in which the sealant isto be used. The iron oxide should be essentially copper free with notover .06% copper present. The FeO content should not be below 23% whilethe fineness of this oxide should be such that not less than 99% willpass through a sieve rated at 300 mesh to the inch.

Calcium carbonate may be substituted for iron oxide in the sameproportions by weight. The calciurn carbonate is preferably of afineness such that 100% Will pass through a sieve rated at 100 mesh perinch while at least 99% will pass through a sieve rated at 300 mesh perinch. The moisture content of this material should not exceed .25% byweight. The fine particle size of the iron oxide and calciurn carbonateis necessary to provide a sealant with good resistance to cracking.

As will be understood by those working in the art softeners may be usedsuch as those set out by J. D. DIanni, J. J. Hoesley and P. S. Greer inan article entitled Oil Extended Synthetic Rubber Including 011 MasterBatched GRS published in the Rubber Age, Inne 1951.

The advantages of the sealant of the invention are obtained by the useof a softener content far above that normally used in compoundingnatural rubber and synthetie rubbery polymers. The following table listswhat is generally considered the maximum usable amount of softener forcertain synthetic rubber stocks based on arts by weight of copolymerused:

Stock: Parts by weight Tire tread stock 60 Tire body stock 50 Tire innertube stock 30\ Butyl inner tube sealant 60 The present invention usessoftener loadings in a range above 80 arts by weight based on the mbberhydrocarbon content. The tackifier content also serves to softem therubber and although listed in the above examples as a tackifier alsocontributes to softening of the final sealant compound. Satisfactory assofteners are petroleum oils, etroleum resins as well as pine 0i1 andthe like. Tackifiers available for the invention include syntheticresins such as coumarone-indene resins, ester gum, rosin and othertackifiers oflered sommercially to the rubber industry.

Several preferred embodirnents of the invention have been described inconsiderable detail but it Will be understood that variations andmodifications may be efiected Within the spirit and scope 0f theinvention as defined in the following claims.

I claim:

1. In a closed pneumatic container the combination of an inner,substantially air impervious linear element comprised of natural rubberand adhered to the inner surface of said liner a puncture sealing membercomprised of a copolymer of an open chain conjugated diolefin with anaryl substituted ethylene monomer copolymerized at a temperature of 14F. to 58 F., havingv at least 25 parts of softener based 011 100 partsby weight of copolymer added to the copolymer in the latex stage and atleast 55 arts of softener based on 100 arts by weight of copolymer addedto the compound after coagulation of the latex.

2. In a pneumatic tire the combination of an inner substantially airimpervious liner element comprised of natural rubber and adhered to theinner surface of said liner a puncture sealing member comprised of acopolymer of an open chain conjugated diolefin with an aryl substitutedethylene monomer copolymerized at a temperature of 14 F. to 58 F. havingat least 25 parts of softener based on 100 parts by Weight of copolymeradded to the copolymer in the latex stage and at least parts of softenerbased on parts by weight of copolymer added to the compound aftercoagulation of the latex.

3. In a pneumatic tire the combination of an inner substantially airimpervious liner element comprised of synthetic rubber and adhered tothe inner surface of said liner a puncture sealing member comprised of acopolymer of an open cha'm conjugated diolefin with an aryl substitutedethylene monomer copolymerized at a temperature of 14 F. to 58 F.,having at least 25 parts of softener based on 100 parts by weight ofcopolymer added to the copolymer in the latex stage and at least 55parts of softener based on 100 parts by weight of copolymer added to thecompound after coagulation of the latex.

4, In a pneumatic tire the combination of an inner substantially airimpervious liner element comprised of a vulcanized rubbery polymericmaterial and adhered to the inner surface of said liner a puncturesealing member comprised of a copolymer of butadiene and styrenecopolymerized at a temperature between 14 F. and 58 F. having at least25 parts of softener based on 100 parts by weight of copolymer added tothe copolymer in the latex stage and at least 55 parts of softener basedon 100 pa1ts by weight of copolymer added to the compound aftercoagulation of the latex.

References Cited in the file of this patent UNITED STATES PATENTS2,406,903 Rethorst Sept. 3, 1946 2,576,968 Pike et a1. Dec. 4, 19512,587470 Herzegh Feb. 26, 1952 2,606884 Mayfield Aug. 12, 1952 2649,425Hlse Aug. 18, 1953 2;664936 Waber Jan. 5, 1954 OTHER REFERENCES DIanm'et al.: Rubber Age; vol. 69, N0. 3; Inne 1951; pp. 317-321.

Rostler: Rubber Age; V01. 69, N0. 5; August 1951; Pp. 559577.

Weinstock et al.: Rubber Age; December 1951; pp. 333-338.

2. IN A PNEUMATIC TIRE THE COMBINATION OF AN INNER SUBSTANTIALLY AIRIMPERVIOUS LINER ELEMENT COMPRISED OF NATURAL RUBBER AND ADHERED TO THEINNER SURFACE OF SAID LINER A PUNCTURE SEALING MEMBER COMPRISED OF ACOPOLYMER OF AN OPEN CHAIN CONJUGATED DIOLEFIN WITH AN ARYL SUBSTITUTEDETHYLENE MONOMER COPOLYMERIZED AT A TEMPERATURE OF 14*F. TO 58*F.,HAVING AT LEAST 25 PARTS OF SOFTENER BASED ON 100 PARTS BY WEIGHT OFCOPOLYMER ADDED TO THE COPOLYMER IN THE LATEX STAGE AND AT LEAST